Department of Psychology and Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Piazza dell'Ateneo Nuovo 1, 20126, Milan, Italy.
University Research Centre in Optics and Optometry, University of Milano-Bicocca (COMiB), Milan, Italy.
Exp Brain Res. 2019 Aug;237(8):2111-2121. doi: 10.1007/s00221-019-05577-0. Epub 2019 Jun 12.
Transcranial direct current stimulation (tDCS) has been widely used for modulating sensory, motor and cognitive functions, but there are only few attempts to induce and change illusory perception. Visual illusions have been the most traditional and effective way to investigate visual processing through the comparison between physical reality and subjective reports. Here we used tDCS to modulate two different visual illusions, namely the Brentano illusion and the glare effect, with the aim of uncovering the influence of top-down mechanisms on bottom-up visual perception in two experiments. In Experiment 1, to a first group of subjects, real and sham cathodal tDCS (2 mA, 10 min) were applied over the left and right posterior parietal cortices (PPC). In Experiment 2, real and sham cathodal tDCS were applied to the left and right occipital cortices (OC) to a second group of participants. Results showed that tDCS was effective in modulating only the Brentano illusion, but not the glare effect. tDCS increased the Brentano illusion but specifically for the stimulated cortical area (right PPC), illusion direction (leftward), visual hemispace (left), and illusion length (160 mm). These findings suggest the existence of an inhibitory modulation of top-down mechanisms on bottom-up visual processing specifically for the Brentano illusion, but not for the glare effect. The lack of effect of occipital tDCS should consider the possible role of ocular compensation or of the unstimulated hemisphere, which deserves further investigations.
经颅直流电刺激（tDCS）已被广泛用于调节感觉、运动和认知功能，但很少有尝试用于诱导和改变幻觉。视觉错觉是通过物理现实与主观报告的比较来研究视觉处理的最传统和最有效的方法。在这里，我们使用 tDCS 来调节两种不同的视觉错觉，即布伦塔诺错觉和眩光效应，目的是在两个实验中揭示自上而下机制对自下而上视觉感知的影响。在实验 1 中，对第一组受试者，真实和假阴极 tDCS（2 mA，10 分钟）应用于左、右后顶叶皮层（PPC）。在实验 2 中，第二组参与者的左、右枕叶皮层（OC）接受真实和假阴极 tDCS。结果表明，tDCS 仅能有效调节布伦塔诺错觉，但不能调节眩光效应。tDCS 增加了布伦塔诺错觉，但仅针对刺激的皮质区域（右 PPC）、错觉方向（向左）、视觉半空间（左）和错觉长度（160mm）。这些发现表明，自上而下机制对自下而上视觉处理存在抑制性调节，特别是对布伦塔诺错觉，但不对眩光效应。枕叶 tDCS 没有效果应该考虑到眼球补偿或未刺激半球的可能作用，这值得进一步研究。
